For a wireless communications network, a common network architecture is formed by a radio access network and a core network, and the radio access network and the core network are connected through an interface. The radio access network is connected to an accessing terminal through a radio interface and provides a service for the terminal.
With the development of a technology, a new network architecture appears, that is, an intermediate node is introduced between an access network node and a core network node. The intermediate node serves as a proxy node between the access network node and the core network node: from the perspective of a core network, the intermediate node functions as an access network node; and from the perspective of an access network node, the intermediate node functions as a core network node.
A long term evolution (Long Term Evolution, hereinafter referred to as LTE) system is used as an example. In the LTE system, some base stations (enhanced NodeB, hereinafter referred to as eNB) are connected to a mobility management entity (Mobility Management Entity, hereinafter referred to as MME) through a gateway (Gateway, hereinafter referred to as GW), but some eNBs are directly connected to the MME. The logical interfaces between the eNB and GW, the GW and MME, and the eNB and MME are the same, and are all S1 interfaces; a directly connected logical interface may exist between eNBs, called an X2 interface. Compared with an S1 interface, a user equipment (User Equipment, hereinafter referred to as UE) may be handed over more quickly from a source eNB to a target eNB through the X2 interface. The handover performed through the X2 interface is called X2 handover.
The eNB may be a common macro base station or a small base station, including a home base station (Home enhanced NodeB, hereinafter referred to as HeNB and Home NodeB, hereinafter referred to as HNB) or a relay node (relay node, hereinafter referred to as RN).
Based on the topology relationship between the source eNB and the target eNB, X2 handover may be classified into the following five cases:
(1) The source eNB and the target eNB are connected to the same GW;
(2) The source eNB is connected to the GW, and the target eNB is connected to the MME;
(3) The source eNB is connected to the MME, and the target eNB is connected to the GW;
(4) The source eNB is connected to a GW, and the target eNB is connected to another GW; and
(5) Both the source eNB and the target eNB are connected to the MME.
In the prior art, in any of the preceding cases, the target eNB sends a UE context release message to the source eNB through the X2 interface after X2 handover. After receiving the UE context release message, the source eNB releases a context-related resource of a UE handed over to the target eNB, where the context-related resource includes all the resources used by the UE on user and control planes in the source eNB.
However, compared with cases (1), (3), and (5), the source GW in cases (2) and (4) also has the context-related resource of the UE handed over to the target eNB. If the scheme of releasing the context of a UE provided in the prior art is used, the source GW does not find that the UE has moved out of the management scope of the source GW during and after X2 handover. As a result, the context-related resource of the UE in the source GW cannot be released, where the context-related resource includes all the resources used by the UE on the user and control planes in the source GW. Therefore, a new UE cannot access a network successfully, and resources are exhausted.